This invention relates to a new method of carbonizing coal as for example the carbonization of metallurgical coal to produce coke which is used in furnaces that produce molten iron. Specifically this new method is an improvement over U.S. Pat. No. 2,922,752 issued to Reintjes; this patent discloses the converting of coal into coke by force-feeding the coal into individual tubes (coking chambers) which are heated in such a way as to have the coal heated indirectly. Since coal is a bad conductor of heat, Reintjes' coking chambers are kept small in diameter (12 in./30.48 cm) in order to make possible to heat the coal effectively; this results in requiring a great multitude of coking chambers with their attendant individual charging mechanisms, valves and controls, in order to achieve a certain productive capacity; such multitude of coking chambers makes a commercial facility uneconomical to construct and complex to operate.
The present invention overcomes the deficiencies of Reintjes by providing an efficient method of making coke in a space (annulus) created between a large diameter (7 ft/2.1 m) tube and a smaller diameter (5 ft./1.5 m) tube, both tubes being heated in such a way as to have the coal heated by the inner wall of the large tube and by the outer wall of the smaller tube. This approach provides a coking chamber with increased surface area for heating to which the coal is exposed; consequently, the number of coking chambers required for the same productive capacity is diminished appreciably when compared to Reintjes, resulting in the reduction of the capital requirement and the simplification of the operation of a commercial cokemaking facility.
For example, to heat 4.7 tons of coal per hour to an average temperature of 1150.degree. F. (621.degree. C.) Reintjes apparatus consisted of thirty (30) coking chambers of 20 feet (6.1 m) in length (see top of Column 5 of Reintjes' patent). In the instant invention two (2) coking chambers of 48 feet (14.6 m) in length will heat 5.6 tons of coal per hour to an average temperature of 1853.degree. F. (1012.degree. C.). Taking all the factors into account this translates to one coking chamber in the instant invention producing the equivalent of about twelve (12) coking chambers of Reintjes.